The variation of microstucture and phase structure of metal Cr and Al powders prepared by high energy mechanical milling was analyzed and investigated.The results show that with the continuous balling the average grai...The variation of microstucture and phase structure of metal Cr and Al powders prepared by high energy mechanical milling was analyzed and investigated.The results show that with the continuous balling the average grain sizes of the brittle Cr powders are gradually decreased,and the diffraction peaks are widened and the peak values lower owing to the interrelation caused by both cold welding and breaking;the tough Al powders exhibit intense cold welding,and most of powders lead to adhesion to ball surface and pot wall,meanwhile,the Al powders subjected to intense deformation have led to many dislocation rings with non dislocation wind up found in the microstructure.展开更多
The powder compaction simulations were performed to demonstrate deformation behavior of particles and estimate the effect of different punch speeds and particle diameters on the relative density of powder by a multi-p...The powder compaction simulations were performed to demonstrate deformation behavior of particles and estimate the effect of different punch speeds and particle diameters on the relative density of powder by a multi-particle finite element model(MPFEM). Individual particle discretized with a finite element mesh allows for a full description of the contact mechanics. In order to verify the reliability of compaction simulation by MPFEM, the compaction tests of porous aluminum with average particle size of 20 μm and 3 μm were performed at different ram speeds of 5, 15, 30 and 60 mm/min by MTS servo-hydraulic tester. The results show that the slow ram speed is of great advantage for powder densification in low compaction force due to sufficient particle rearrangement and compaction force increases with decrease in average particle size of aluminum.展开更多
A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energ...A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.展开更多
The influence of high energy ball milling on Al 30Si powder and ceramic particulate SiC was studied by means of SEM, XRD and DSC. The results show that Al 30Si powder and their microstructure are obviously refined aft...The influence of high energy ball milling on Al 30Si powder and ceramic particulate SiC was studied by means of SEM, XRD and DSC. The results show that Al 30Si powder and their microstructure are obviously refined after high energy ball milling process. The alloy powder and SiC p stick closely to each other without interfacial reaction. DSC results detect no reaction but relaxation of the samples. So high energy ball milling can be used as an effective method for ceramic particulate pre treatment in the fabrication of MMC.展开更多
After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). Accordi...After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). According to the patterns of reaction peaks on the DTA curves, the activation energy of each reaction was calculated. The experimental results of DTA show that the synthesis reaction of Al Ti C powder mixture can be enhanced after high energy milling. The longer the milling time, the lower the reaction temperature. The synthesis reaction of TiC is transformed from Ti+C→TiC to Al 3Ti+C→TiC+3Al with long period milling. Meanwhile, the activation energy of the reaction reduces with increasing milling time. The effect of milling time on reduced activation energy for low temperature region is more significant than that for high temperature region.展开更多
Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show tha...Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show that chemical composition of the master alloy is the key factor which controls the chemical composition of the compound phases in nanometer powders at given evaporating temperature, the compound phases with high Fe mole fraction will form with increasing of Fe content in master alloy. Only Al 13 Fe 4, FeAl 2 and Al 2Fe compound phases form in nanometer powders in present experiment, changing of the pressure of Ar can only alter relative amounts of the compound phases in the powders. Nanometer particles with inhomogeneous tissue were obtained, which is very different from that of pure Al and Fe nanometer particles. When mole fraction of Fe in particles increases, the inhomogeneity is enhanced. [展开更多
β-SiC nanoparticle reinforced Al matrix(nano-SiCp/Al) composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures ...β-SiC nanoparticle reinforced Al matrix(nano-SiCp/Al) composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures of the as-prepared composites were observed by scanning electronic microscopy(SEM), and the mechanical properties were characterized by tensile strength measurement and Brinell hardness test. The experimental results revealed that the tensile strength of the composite with the addition of 5wt%-SiC nanoprticles could be increased to 215 MPa, increasing by 110% compared with pure Al matrix. Comparative experiments reflected that the-SiC nanoprticles showed significant reinforcement effect than traditional-SiC micro-sized particles. The preparation process and sintering procedure were investigated to develop a cost effective preparation strategy to fabricate nano-SiCp/Al composite.展开更多
In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor w...In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor was used. The samples were produced using powder metallurgy process, and then subjected to natural aging where heat treatment was conducted for all samples together at 550°C for 3 hours before quenching in water. Then, the samples were left at room temperature for 936 hours (39 days) to allow traces atoms to diffuse and form coherent phases which increase the hardness. It was found that the hardness was firstly increased with time for about 300 hours after the quenching time, and then it tends to remain constant after that. However, the hardness drop at overage stage was not observed until the end of 936 hours. To get a full analysis of the natural aging we used design of experiment tool to study the effect of %Cu, %Ni and aging time on the hardness. The results showed that the hardness was influenced significantly by all considered factors and interactions between them.展开更多
The interface of the SiCp/Al composites produced by powder metallurgy processing involving hotpressing above the matrix solidus temperature has been investigated by means of TEM. Several kinds of interfaces between th...The interface of the SiCp/Al composites produced by powder metallurgy processing involving hotpressing above the matrix solidus temperature has been investigated by means of TEM. Several kinds of interfaces between the reinforcements and the matrix in the composite, including the clean interfaces, the faceted interfaces and the slight reaction intedeces, are presented. And most of interfaces belong to the slight reaction interfaces which are composed of the Al with different orientation from the Al matrix near the interface zone and particte-like substances produced by MgAl2O4 spinels and展开更多
Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness ...Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.展开更多
The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+Y powder. Laser cladding was carried out with a 5 kW continuous wave CO2 laser by melting the preplaced powder mixture of Al and Y. F...The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+Y powder. Laser cladding was carried out with a 5 kW continuous wave CO2 laser by melting the preplaced powder mixture of Al and Y. Following laser cladding, the cladding zone was characterized by a detailed microstructural observation and phase analysis. Moreover, the microhardness and element distribution were evaluated in detail. The surface modified layer consists of Mg17Al12 and Al4MgY phases, while α-Mg and Mg17Al12 in the substrate. The microhardness of the cladding zone was significantly enhanced as high as HV122180 as compared to HV6080 of the substrate region. The maximal hardness about HV224 is in the interface due to the formation of intermetallic Mg17Al12 phase. The microstructure is refined and Mg diffuses into the cladding material which leads to the formation of Mg17Al12.展开更多
Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advance...Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advanced zero-valent iron are highly effective for degradation of chlorinated organic compounds. The efficiency of degradation for carbon tetrachloride and perchloroethylene is higher than 99% within a period of 2 h. The efficiency of degradation for trichloroethylene by MAF after storing for one month is equivalent to that by freshly prepared nano-size zero-valent iron particles.展开更多
文摘The variation of microstucture and phase structure of metal Cr and Al powders prepared by high energy mechanical milling was analyzed and investigated.The results show that with the continuous balling the average grain sizes of the brittle Cr powders are gradually decreased,and the diffraction peaks are widened and the peak values lower owing to the interrelation caused by both cold welding and breaking;the tough Al powders exhibit intense cold welding,and most of powders lead to adhesion to ball surface and pot wall,meanwhile,the Al powders subjected to intense deformation have led to many dislocation rings with non dislocation wind up found in the microstructure.
基金supported by a grant-in-aid for the National Core Research Center Program from the Ministry of Education Science & Technology,Koreathe Korea Science & Engineering Foundation (No.R15-2006-022-03003-0)
文摘The powder compaction simulations were performed to demonstrate deformation behavior of particles and estimate the effect of different punch speeds and particle diameters on the relative density of powder by a multi-particle finite element model(MPFEM). Individual particle discretized with a finite element mesh allows for a full description of the contact mechanics. In order to verify the reliability of compaction simulation by MPFEM, the compaction tests of porous aluminum with average particle size of 20 μm and 3 μm were performed at different ram speeds of 5, 15, 30 and 60 mm/min by MTS servo-hydraulic tester. The results show that the slow ram speed is of great advantage for powder densification in low compaction force due to sufficient particle rearrangement and compaction force increases with decrease in average particle size of aluminum.
基金supported by the National Natural Science Foundation of China,China(Grant Nos.U20B2018,U21B2086,11972087)。
文摘A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.
基金supported by the Key Laboratory of Micro-systems and Micro-structures Manufacturing of Ministry of Education,Harbin Institute of Technology,China(No.2020KM005)the Natural Science Foundation of Heilongjiang Province,China(No.YQ2020E030)。
文摘The influence of high energy ball milling on Al 30Si powder and ceramic particulate SiC was studied by means of SEM, XRD and DSC. The results show that Al 30Si powder and their microstructure are obviously refined after high energy ball milling process. The alloy powder and SiC p stick closely to each other without interfacial reaction. DSC results detect no reaction but relaxation of the samples. So high energy ball milling can be used as an effective method for ceramic particulate pre treatment in the fabrication of MMC.
文摘After milling in a high energy ball miller for various times, the synthesis reaction process of the Al Ti C powder mixture were investigated by difference thermal analysis (DTA) and X ray diffractometry (XRD). According to the patterns of reaction peaks on the DTA curves, the activation energy of each reaction was calculated. The experimental results of DTA show that the synthesis reaction of Al Ti C powder mixture can be enhanced after high energy milling. The longer the milling time, the lower the reaction temperature. The synthesis reaction of TiC is transformed from Ti+C→TiC to Al 3Ti+C→TiC+3Al with long period milling. Meanwhile, the activation energy of the reaction reduces with increasing milling time. The effect of milling time on reduced activation energy for low temperature region is more significant than that for high temperature region.
文摘Nanometer powders of Al Fe alloy were prepared by gas evaporation. The formation regularity of the phases in the as prepared powders and the morphology of the particles were examined. The experimental results show that chemical composition of the master alloy is the key factor which controls the chemical composition of the compound phases in nanometer powders at given evaporating temperature, the compound phases with high Fe mole fraction will form with increasing of Fe content in master alloy. Only Al 13 Fe 4, FeAl 2 and Al 2Fe compound phases form in nanometer powders in present experiment, changing of the pressure of Ar can only alter relative amounts of the compound phases in the powders. Nanometer particles with inhomogeneous tissue were obtained, which is very different from that of pure Al and Fe nanometer particles. When mole fraction of Fe in particles increases, the inhomogeneity is enhanced. [
基金Funded by the Research Collaborative Innovation Project of Jiangsu Province,China(BY2009129)the Science and Technology Project of Suzhou,China(SYG0905)
文摘β-SiC nanoparticle reinforced Al matrix(nano-SiCp/Al) composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures of the as-prepared composites were observed by scanning electronic microscopy(SEM), and the mechanical properties were characterized by tensile strength measurement and Brinell hardness test. The experimental results revealed that the tensile strength of the composite with the addition of 5wt%-SiC nanoprticles could be increased to 215 MPa, increasing by 110% compared with pure Al matrix. Comparative experiments reflected that the-SiC nanoprticles showed significant reinforcement effect than traditional-SiC micro-sized particles. The preparation process and sintering procedure were investigated to develop a cost effective preparation strategy to fabricate nano-SiCp/Al composite.
文摘In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor was used. The samples were produced using powder metallurgy process, and then subjected to natural aging where heat treatment was conducted for all samples together at 550°C for 3 hours before quenching in water. Then, the samples were left at room temperature for 936 hours (39 days) to allow traces atoms to diffuse and form coherent phases which increase the hardness. It was found that the hardness was firstly increased with time for about 300 hours after the quenching time, and then it tends to remain constant after that. However, the hardness drop at overage stage was not observed until the end of 936 hours. To get a full analysis of the natural aging we used design of experiment tool to study the effect of %Cu, %Ni and aging time on the hardness. The results showed that the hardness was influenced significantly by all considered factors and interactions between them.
文摘The interface of the SiCp/Al composites produced by powder metallurgy processing involving hotpressing above the matrix solidus temperature has been investigated by means of TEM. Several kinds of interfaces between the reinforcements and the matrix in the composite, including the clean interfaces, the faceted interfaces and the slight reaction intedeces, are presented. And most of interfaces belong to the slight reaction interfaces which are composed of the Al with different orientation from the Al matrix near the interface zone and particte-like substances produced by MgAl2O4 spinels and
文摘Ti6Al4V powder compaction was performed by using magnetic pulse compaction in air at 200℃.Effects of process parameters such as voltage,capacitance,discharge times on the microstructure,compressive strength,hardness and relative density of compacts were investigated.The experimental results show that the relative density,hardness and compressive strength of compacted specimens increase with increasing voltage.In addition,the relative density and compressive strength of compacted specimens increase with the augmentation of capacitance in the range investigated.The relative density increases,the hardness firstly increases and then tends to be a fixed value;and the compressive strength firstly increases and then decreases from one to five times compaction.Both values of the hardness and compressive strength reach the maxima of HRA 69.1 and 1 062.31 MPa,at three times compaction,respectively.There are pores in and between particles.
文摘The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+Y powder. Laser cladding was carried out with a 5 kW continuous wave CO2 laser by melting the preplaced powder mixture of Al and Y. Following laser cladding, the cladding zone was characterized by a detailed microstructural observation and phase analysis. Moreover, the microhardness and element distribution were evaluated in detail. The surface modified layer consists of Mg17Al12 and Al4MgY phases, while α-Mg and Mg17Al12 in the substrate. The microhardness of the cladding zone was significantly enhanced as high as HV122180 as compared to HV6080 of the substrate region. The maximal hardness about HV224 is in the interface due to the formation of intermetallic Mg17Al12 phase. The microstructure is refined and Mg diffuses into the cladding material which leads to the formation of Mg17Al12.
文摘Micro-scale Al-Zn-Mg/Fe composite powders (MAF) with high reactivity and good storage properties were prepared by reducing iron onto the surface of Al-Zn-Mg alloy powders. Experimental results show that MAF as advanced zero-valent iron are highly effective for degradation of chlorinated organic compounds. The efficiency of degradation for carbon tetrachloride and perchloroethylene is higher than 99% within a period of 2 h. The efficiency of degradation for trichloroethylene by MAF after storing for one month is equivalent to that by freshly prepared nano-size zero-valent iron particles.
